Lord Ashcroft’s new polling – and the accompanying report, Project Red Dawn – contains numerous insights into the state of the modern Labour Party. He laid out several of them for us this morning, not least Labour’s fundamental problem that their remaining core support is losing interest in winning elections.

There is one particular topic that I think is worth focusing on a little more. It’s the question of how sticky those who defected from Labour to other parties are – ie are they likely to stay gone, or might they be persuaded to come back?

When people who used to vote for you start to consider another Party, it’s a problem. When they actually do leave you and go elsewhere, it is a disaster. If you can’t work out how to win them back, then the issue may become terminal.

Voters who abandoned the Conservatives for UKIP during the last parliament were a clear, well-reported challenge for Tory strategists. They were sufficiently numerous that for a long time it looked like their loss might cost Cameron the General Election. But it seems a relatively large chunk of them were persuaded to return – not least by a well-targeted message about the risk of a Labour/SNP coalition. The Conservatives would have been happier not to suffer a mass defection in the first place, but they were able to rectify it to a sufficient extent.

To assess the stickiness of ex-Labour defectors, we first need to look at who they are. The crucial divide which Lord Ashcroft identifies is in who they defected to – the Conservatives or UKIP?

As we can see, those who voted Conservative were somewhat less likely to be lifelong Labour voters (49 per cent) than those who voted for UKIP (72 per cent). These voters, those in the top row of the chart, are the very worst to lose – once you have broken a lifelong loyalty, it can never be completely restored.

Tribal voters have major psychological barriers to breaking with their tribe – their personal identity, their definition of their family, their sense of belonging and their learned dislike of the other side all need to be overcome if they are to switch their vote. I suspect that is one reason why these lifelong voters found it a bit easier to vote UKIP than Tory – hatred of Tories often runs deep, fed by a long history, whereas UKIP have relatively less emotional baggage:

But in either case, Conservative or UKIP, it should worry Labour that such a high proportion of those who abandoned them came from their hard core of lifelong Labour voters. For once that taboo has been broken, and it turns out lighting doesn’t really strike you down if you vote another way, then the power of the illusion swiftly dissipates. At the very least, these voters have turned from committed Labourites to floating voters – and many have broken their ties of identity completely:

The really bad news here is that defection is habit-forming – only a minority of defectors still think of themselves as inherently Labour people. Like Humpty Dumpty, once innate, cultural loyalties are broken, it is nigh-on impossible to put them back together again – at least in a short period of time like a five year parliamentary term.

But while Labour has lost much of the hold it once had on these voters, it is still faced with the challenge of winning them back.

All defectors do at least have one top motive in common:

But it’s unlikely that the departure of Ed Miliband will be enough to bring them flooding back. Look at those second and third reasons for switching – these are fundamental questions of competence (“I was worried Labour would spend and borrow too much”) and identity (“Labour no longer seemed to stand up for people like me”).

Many have observed that a primary difficulty for the next leader of the Opposition will be appealing to the variety of voters who have abandoned the party – to the SNP in Scotland, to UKIP in various Midlands and Northern Labour heartlands and to the Conservatives right across the South of England – while hanging on to their existing core vote. This is because the demands of each group are not only different, they are contradictory.

Here are some examples:

Spending: 69 per cent of those who defected to the Conservatives think further spending cuts are needed. 71 per cent of defectors to UKIP think spending cuts have gone too far.

Welfare: 80 percent of defectors to the Conservatives think the benefits system is too generous. 54 per cent of defectors to UKIP think so, while 69 per cent of Labour loyalists oppose any further cuts to welfare.

That is a circle which cannot be squared. Whoever the new Labour leader might be will swiftly become tangled up in a web of contradictory demands. Only one candidate, Jeremy Corbyn proposes to just pursue ideology regardless of polling. This too is unfortunate for Labour, for he is ideologically pro-immigration, the only topic on which loyalists and defectors are united: in opposition.

In short, if you thought Labour were having a bad week, it just got worse. Even before they embarked on their leadership contest, they had suffered severe damage to their voter base. Even the best of Labour leaders would have found this polling intimidating.